Joint replacement surgery is quite common and it enables many individuals to function normally when they otherwise would not be possible to do so. Typically, an artificial joint includes metallic, ceramic and/or plastic components that are fixed to existing bone. One type of joint is a condylar or condyloid joint (ellipsoidal joint) in which an ovoid articular surface or condyle is received into an elliptical cavity. A condylar joint is better called bicondylar due to two distinct surfaces on one bone articulating with corresponding distinct surfaces on another bone. There are two male surfaces on one bone and are of the same type (e.g., ovoid).
One of the more common joints that undergoes replacement surgery is the knee. Knee arthroplasty is a well known surgical procedure by which a diseased and/or damaged natural knee joint is replaced with a prosthetic knee joint. Traditionally the joint surfaces associated with implant components are approximated by toroidal or donut shaped surfaces on both the insert and the condylar surfaces of the femoral component which transfer load from the femur to the tibia through an insert component. The total joint, once implanted, is stabilized and controlled in part by these surfaces and in part by the soft tissues surrounding and encapsulating the knee.
Total knee arthroplasty (TKA) devices can fail for reasons such as aseptic loosening, instability, or infection. Failure usually requires revision surgery. Revision implants have been developed that include a post on the polyethylene tibial component that articulates within a recess (intercondylar box) in the femoral component. The objective of this so called constrained condylar knee (CCK) implant is to rely on contact between the box and the post within the joint itself to restrain and limit rotation of the knee (varus/valgus rotations). This constraint is also beneficial in primary TKA if the soft tissues cannot be balanced to achieve an adequately stabilized and controlled joint.
In addition, other joints that have similar condyle structures to the knee, such as the elbow and ankle, etc., likewise suffer from the same limitations and deficiencies described above with reference to the knee. It would thus also be likewise desirable to produce an elbow or ankle replacement with an articular surface designed to gradually shift the contact point outwardly as more varus/valgus motion is initiated, thus increasing the restoring moment at the joint.
Based on the aforementioned, there is a need for prosthetic condylar joints with articulating bearing surfaces having a translating contact point during rotation (varus/valgus) thereof.